Conventionally, there has been known a MOSFET which includes a semiconductor base substrate where a super junction structure is formed of an n-type column region and a p-type column region (see patent document 1, for example).
In this specification, “super junction structure” means a structure where an n-type column region and a p-type column region are alternately and repeatedly arranged as viewed in a predetermined cross section.
As shown in FIG. 14, a conventional MOSFET 900 includes: a semiconductor base substrate 910 having n-type column regions 914, p-type column regions 916, a p-type base region 918 formed on surfaces of portions of the n-type column regions 914 and whole surfaces of the p-type column regions 916, and n-type source regions 920 formed on a surface of the base region 918 and where a super junction structure is formed of the n-type column regions 914 and the p-type column regions 916; gate electrodes 926 formed on the base region 918 sandwiched between the source regions 920 and the n-type column regions 914 by way of gate insulation films 924. In FIG. 14, symbol 930 indicates a source electrode, and symbol 932 indicates a drain electrode.
In the conventional MOSFET 900, the n-type column region 914 and the p-type column region 916 are formed such that a total amount of a dopant in the n-type column regions 914 is equal to a total amount of a dopant in the p-type column regions 916. That is, the n-type column regions 914 and the p-type column regions 916 are well-balanced with each other in terms of charge.
The conventional MOSFET 900 includes the semiconductor base substrate 910 where the super junction structure is formed of the n-type column regions 914 and the p-type column regions 916 thus providing a switching element which has a low ON resistance and a high withstand voltage.